System and method for irrigation control

ABSTRACT

A method of controlling the duration of irrigation is described, comprising compiling a database that includes information relating to historical evapo-transpiration rates for a plurality of sectors (preferably identified by zip code) located within a geographical area. Period Reduction Factors for each sector are derived. Parameters are entered into the controller including a Maximum Irrigation Duration, a sector identifier; and the current date. The Maximum Irrigation Duration is adjusted by multiplying the Maximum Irrigation Duration by a Period Reduction Factor for the current period associated with the sector that has been identified by the user, to obtain an Actual Irrigation Duration. The irrigation system is caused to irrigate for the Actual Irrigation Duration during the current period.

BACKGROUND

The present invention relates to a system and method for regulating theoperation of an irrigation system. More particularly, the inventionpertains to a system and method for regulating the operation of anirrigation system which is responsive to user programmed information.

Automatic irrigation systems such as those employed for landscape andagricultural watering are well known in the art. Typical irrigationsystems use a means of controlling the watering cycles via an automaticcontroller. The need to control watering cycles due to seasonal changingenvironmental conditions is important for saving costs, optimizinggrowing conditions, and preventing unsafe conditions.

Typically, a user will enter instructions into a microprocessor basedcontroller that will cause the irrigation system to start irrigation ata certain time, on certain days, for a certain duration, according tothe user's instructions. Irrigation may be based on “zones” in which agroup of sprinkler heads discharge in unison, or sequentially, or acombination of both.

Typically, a user who programs the microprocessor in the summer month ofJuly to deliver an irrigation event of a certain duration on certaindays from a particular irrigation system, would, if reminded to attendto the issue, reduce that duration over the fall, winter, and springmonths to take account of changing seasonal environmental conditionsthat can be expected to prevail in the vicinity of the irrigationsystem, and the user might reduce the duration accordingly each month,or shorter period, before increasing it again. Typically, however, manyusers tend to forget to downwardly adjust the irrigation duration afterthe hot summer months to account for the reduced evapo-transpirationrates over the following months. At best, a user will typically rememberto adjust irrigation for some months or shorter period, but not others.As a result, the irrigation system continues to discharge water inirrigation during the fall, and winter at a rate that was selected to besuitable during the summer, or some other time that is inappropriate.This can be very wasteful, not to mention destructive in the case ofcertain crops, grasses, flowers, and shrubs that react adversely to overor under watering.

Consequently, solutions have been developed for taking into accountactual environmental conditions prevailing, and for automaticallyadjusting irrigation duration to take account of changed conditions inreal time. These solutions typically employ a sensor that monitorschanges in environmental conditions in real time. A sensor may belocated near an associated controller, and may be linked to thecontroller either by wireless communication or by physical connection.Such a sensor may measure actual precipitation, actual temperatures,actual wind speed, soil moisture, humidity, and other environmentalfactors, all in real time. Based on these measurements which aretransmitted back to the controller, the controller uses preprogrammedlogical algorithms and decides how to adjust a preprogrammed irrigationschedule to account for changed environmental conditions. For example,if high temperatures and dry conditions are recorded, irrigationduration may be increased. If wet or cold conditions are noted,irrigation may be reduced or suspended altogether.

However, such sensor based systems have drawbacks and disadvantages.They are notoriously complex, and difficult to calibrate and install.Typically, weather sensors are mounted where they are exposed to theelements and once mounted are not easily adjusted or manipulated. Theyadd significantly to the cost of a controller system that must bepre-programmed to take into account a host of new variables and logicsubroutines. They are prone to malfunction, and difficult to maintain inoperation.

Accordingly, there is a need in the art for an irrigation controllerthat may be sold and used universally, that is easy to use, that isinexpensive to manufacture, that is easy to install, initialize,maintain, and operate, and that yet takes account of the fact thatseasonal environmental conditions vary during the year in anylocation—and that, accordingly, enables the amount of irrigation in anylocation to be automatically varied for efficient use of the system. Thepresent invention addresses these and other needs.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the invention, there is describedan irrigation controller suitable for use in any part of the world, thattakes into account average environmental changes over the course of ayear, but that is simple to use and inexpensive to make.

In one aspect, the invention is a controller for controlling anirrigation schedule in an irrigation system that includes a plurality ofsprinkler heads connected via a plurality of conduits to a water source.The controller comprises a database that includes information relatingto historical evapo-transpiration (“ET”) rates for a plurality ofsectors located within a geographical area. The information includesPeriod Reduction Factors for each sector. The Period Reduction Factorsare a compilation (for each period) of the ratio of ET rate for thecurrent period divided by the maximum ET rate that occurs during theyear in the location of the controller. The controller further includesan input means for permitting a user to enter irrigation parameters intothe controller, wherein the parameters include a Maximum IrrigationDuration (“Dmax”, the maximum irrigation duration, chosen to coincidewith the period of maximum ET rate), an identifier for identifying thesector in which the irrigation system is located, and the current date.A microprocessor is configured to adjust the Maximum Irrigation Durationthat has been entered into the controller by multiplying the MaximumIrrigation Duration by a Period Reduction Factor for the current period,associated with the sector that has been identified by the user, toobtain an Actual Irrigation Duration (“Dactual”) for the current periodfor the identified sector. The microprocessor is configured to cause theirrigation system to irrigate for the Actual Irrigation Duration duringthe current period, rather than the Dmax, which will only occur in theperiod of highest ET rate.

In a further aspect of the invention, the microprocessor is configuredto sequentially recalculate the Actual Irrigation Duration in each newperiod by applying the Period Reduction Factor associated with the newperiod, and causing the irrigation system to irrigate for the ActualIrrigation Duration during the new current period. In a preferred aspectof the invention, the period associated with the Period Reduction Factoris a day.

In yet a further facet, the invention is a method of controlling theduration of irrigation by an irrigation system that includes a pluralityof sprinkler heads connected via a plurality of conduits to a watersource. The method comprises compiling a database that includesinformation relating to historical evapo-transpiration rates for aplurality of sectors located within a geographical area. A further stepincludes deriving, from the information, Period Reduction Factorsapplicable over a year for each sector. Irrigation parameters areentered into the controller, wherein the parameters include, a MaximumIrrigation Duration, an identifier for identifying the sector in whichthe irrigation system is situated, and the current date. Thereafter theMaximum Irrigation Duration is adjusted by multiplying the MaximumIrrigation Duration by a Period Reduction Factor for the current periodassociated with the sector that has been identified by the user, toobtain an Actual Irrigation Duration for the current period for theidentified sector. Finally, the irrigation system is caused to irrigatefor the Actual Irrigation Duration during the current period.

In a further aspect, entering a sector identifier into the controllerincludes entering a zip code, and the period associated with the PeriodReduction Factor is one day.

Finally, in a yet a further aspect, adjusting the Maximum IrrigationDuration includes sequentially recalculating the Actual IrrigationDuration in each new period by applying the Period Reduction Factorassociated with each new period, and causing the irrigation system toirrigate for the Actual Irrigation Duration during the new currentperiod.

These and other advantages of the invention will become more apparentfrom the following detailed description thereof and the accompanyingexemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an irrigation system having features ofthe present invention

FIG. 2 is a schematic view of an irrigation controller as exemplified inFIG. 1

FIG. 3 is a graph of average evapo-transpiration rates in five differentgeographical sectors in California, over the period of one year.

FIG. 4. is a graph of Monthly Period Reduction Factors for the sectorFresno, Calif.

FIG. 5 is a flow diagram showing steps taken in an aspect of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, which are provided for exemplificationand not limitation, a preferred embodiment of an irrigation controlleris described having features of the present invention.

With respect to FIG. 1, a typical irrigation system 20 includes aplurality of sprinkler heads 22, all linked by conduits 24 to a source26 of water pressure, the heads being configured to discharge water ontoa surrounding landscape either in unison, or one after the other, or ina combination of both. This system may include a number of “zones,” inwhich sprinkler heads are dedicated to act in unison in different partsof a landscape. The overall system may be controlled by a singleelectronic controller 28, which activates water to flow in differentportions of the system 20 at different times, and for selecteddurations.

In this context, a preferred embodiment of the present invention isdescribed with respect to FIGS. 1-4. A preferred embodiment provides anirrigation system 20 that automatically adjusts the amount of water tobe discharged by the system onto a surrounding landscape, according toanticipated environmental conditions in the vicinity of the system. Asprinkler controller 28 is provided that harnesses a microprocessor 30.(FIG. 2, showing the microprocessor schematically within thecontroller.) The controller also includes input means 32 for enteringparameters such as the present time and date, the times of day tocommence irrigation in each zone, the duration for an irrigation event,and the like into the microprocessor. It also includes an LCD screen 33to facilitate entry of parameters. The controller 28 is operativelyconnected with conduits 24 that lead water from a supply 26 to aplurality of sprinkler heads 22 forming part of the irrigation system20. The microprocessor 30 is configured to interpret instruction datathat has been input by a user, and consequently to initiate irrigationvia the conduits 24 according to such data, most particularly tocommence irrigation and then to terminate irrigation after anappropriate irrigation duration has been completed. Such irrigationinitiation is achieved through switched valves 27 that are electricallyoperated and are interposed between the controller 28 and the watersupply 26, and operatively connected to the controller 28 via electricalwires 23.

Importantly in the present invention, the microprocessor 30 alsoincludes a database 34 configured to enable the controller 28,independently of the user, to adjust the duration of irrigation for anirrigation event that has been instructed by the user. This adjustmentis directed at reducing the amount of water discharged during irrigationfor periods of the year when the evapo-transpiration (“ET”) rate in thevicinity of the system 20 is lower than at its peak level. The peaklevel typically occurs some time in June through August of any year inthe northern hemisphere. Evapo-transpiration is a term used to describethe sum of evaporation and plant transpiration from the earth's landsurface to atmosphere. Evaporation accounts for the movement of water tothe air from sources such as the soil, canopy interception, andwaterbodies. Transpiration accounts for the movement of water within aplant and the subsequent loss of water as vapor through stomata in itsleaves. Evapo-transpiration is an important part of the water cycle.Historical records of the ET rate for the United States have been keptand are available from a number of sources, including government managedweather stations such as CIMIS (California Irrigation ManagementInformation System, maintained by the California Department of WaterResources), CoAgMet maintained by Colorado State University-AtmosphericSciences, AZMET maintained by University of Arizona-Soils, Water andEnvironmental Science Department, New Mexico State University-Agronomyand Horticulture, and Texas A&M University-Agricultural EngineeringDepartment. Although slight variations in the methods used to determinethe ET values do exist, most ET calculations are based on the followingenvironmental factors: temperature, solar radiation, wind speed andhumidity. A typical plot of average evapo-transpiration rates againsttime for different cities in California in the United States over theperiod of a year is shown in FIG. 3.

In a preferred aspect of the invention, the database 34 is derived fromhistorical records of the ET rate over a year throughout a geographicalarea, preferably throughout the United States, and also preferablythroughout any part of the world in which historical ET rate records areknown and where the irrigation system 20 may be used. The geographicarea for which the database 34 is compiled is preferably broken downinto a plurality of smaller sectors, each sector being identified forexample by the name of a nearby town, or by county name, or even bystate, where the ET rates are relatively uniform, but most preferablymay be identified by a postal zip code as a small area within which theET rates are likely to be uniform. Thus, in a preferred embodiment, thedatabase 34 is compiled to reflect the average ET rate in each postalzip code area in the United States for a monthly, weekly, or shortertime period, over the duration of a year. While a month is a usefulperiod of time in which to capture the changes in ET rate in a sector, ahalf-monthly period provides a smoother transition over the course of ayear, and a weekly or daily period provides an even smoother transition.Daily average ET rates are also available in the historical record, andthese rates may be used where it is desirable to follow a precisetransition over the course of a year in short increments. For example,in FIG. 3, the ET rates for different parts of California are shown oncurves that are smoothed and from which daily ET rates can be extracted.Similar records are available throughout the United States and othercountries.

It will be understood that in a country such as the United States, manyzip codes that are relatively closely situated will share the same ETdata over the course of a year, but this fact need does not alter theease with which each zip code may be assigned the appropriate ET datafrom historical sources. To this end, although the controller 28 maycall for the entire zip code to be entered by a user, the database maybe based on only the first three digits of a zip code, thus giving aless detailed breakdown of ET rates, although no less effective.

Once the above described data is assembled for a geographical area, itis processed by performing the following steps for each sector (e.g.,zip code):

-   -   a) Identifying the maximum period-average ET rate that occurs in        a year, “ETmax” (typically occurring some time June through        August in the northern hemisphere);    -   b) Identifying the historical period-average ET rate for each        period of the year, “ETperiod.”    -   c) Dividing ETperiod by ETmax, to provide a Period Reduction        Factor for each period of the year, the “PRF” for each period.

As used above, the term “period” may refer to the period of a month,although a half-monthly, weekly, or even daily period may apply whereappropriate.

Thus, preferably before any instructions have been entered into themicroprocessor 30 by the user, the manufacture has compiled and storedin the database 34 an array of information in which each sector(preferably, zip code) in a geographical area has, associated with it, aplurality of PRFs—one for each period of the year whether the period bea month, a half-month, a week, or a day. (See, FIG. 4.) It will beappreciated that alternative methodologies may be used to assemble thedatabase 34. For example, the ET rates themselves may be entered intothe database, in which an algorithm may be selected to extract therelevant PRF for application, but eventually an applicable PRF isderived from data within the microprocessor and all such methodologiesare contemplated as falling within the scope of the invention.

When the user purchases and installs an irrigation control system 20having features of the present invention, the controller 28 calls forcertain information via the LCD screen 33, by prompting the user toenter the information sequentially via the input means 32. (FIG. 2.) Inaddition to the usual start times for each irrigation event in each of aplurality of zones, one parameter that the user will be requested toenter in conjunction with each start time is the Maximum IrrigationDuration (“Dmax”) for each irrigation event that the user wishes tooccur during the period that the ET rate will be greatest in thelocation where the control system is being installed. For example,although the user may be installing his unit in March, the controllerwill ask him to enter the maximum irrigation duration (Dmax) that hewishes to apply at the peak of summer when the ET rate is greatest.Another parameter that the user will be requested to enter is thecurrent date, and another is the identity of the sector in which thesystem 20 is being set up to operate. For a system intended to operatein the United States, this latter parameter will preferably be thepostal zip code in which the system is installed. Once the durationDmax, the current date, and sector identification are entered, themicroprocessor 30 performs the following adjustments to take intoaccount the inevitable seasonal changes, and the changing ET rates, overthe duration of a year. Based on the current date, the microprocessorselects the appropriate PRF for the applicable sector from the database34. The microprocessor then computes an Actual Irrigation Duration(“Dactual”) for the current period by multiplying the maximum duration,Dmax, entered by the user, by the PRF for that period obtained from thedatabase 34. Thus, in the period of January, for example, when the ETrate for a particular sector may be only 16% of the maximum summer ETrate in that sector (so that the PRF for January is 16%), the ActualIrrigation Duration, Dactual, will be computed to be 16% of Dmax. (SeeFIG. 4). The microprocessor 30 then sets the applicable duration forcurrent irrigation events to be the Actual Irrigation Duration, Dactual,and not the maximum irrigation duration, Dmax. For other or shorterperiods, the same principle will apply. Then, when the time arrives forirrigation on any day, the microprocessor 30 causes the irrigationsystem to irrigate for a period of time Dactual rather than Dmax. Thisprocess is exemplified in FIG. 5.

Moreover, after the current “period” has passed (as noted, “period maybe month, half month, week, day or other suitable time period), themicroprocessor 30 is configured to sequentially recalculate the ActualIrrigation Duration in each new period by applying the Period ReductionFactor (PRF) associated with each new period, and causing the irrigationsystem to irrigate for the resulting Actual Irrigation Duration(Dactual) during the new current period. (See, FIG. 5.) For example, thecurves of ET rate in FIGS. 3 and 4 show smoothed curves from which theDactual may be derived on a daily basis.

It will be appreciated that, in use, after the above procedure ofinformation entry and duration adjustment has been completed in a periodthat does not coincide with maximum ET rate, a user may monitor theactual irrigation duration, Dactual, caused by the controller accordingto the above described process. After observing the actual irrigationdurations, it is possible that a user may conclude that insufficientwater (or too much water) is being caused to discharge by the controllerin each irrigation event. Under these circumstances, a user may manuallyalter the Dmax that he had previously input, so that the current Dactualincreases or reduces proportionally. When the user is satisfied that theDactual for the current period is acceptable, he can reasonably assumethat the Dactual that will be caused in the period of greatest ET rate(that will in effect be 100% of Dmax) will be appropriate for thatperiod also. Thus, by a series of small initial adjustments, even duringa period when maximum ET rate does not exist, a user may achieve anoptimal rate of irrigation that applies over the period of a whole year.

In the manner described, once the data entries have been made andadjustments are concluded, it will be appreciated that themicroprocessor continually adjusts the irrigation duration for anyindividual sprinkler system to take into account the historic variationin period average ET rates over the period of a year, each adjustmentbeing made incrementally after a period of time which may be a month, ahalf month, a week, or a day, depending on the requirements of theirrigation project. Preferably, use of the smooth ET rate and PRF curvesexemplified in FIGS. 3 and 4 would permit adjustment to be made on adaily period basis.

The invention thus has the advantage of efficiently and rationallyapplying a modification in water irrigated onto a landscape toaccommodate the seasonal changes in ET rate of a particular sector. Theinvention has versatility in that it may be sold, with a preprogrammeddatabase 34 that includes either a table of Period Reduction Factors(PRFs), or the information necessary (e.g. ET rates) to extract, via analgorithm, PRFs in any sector based, preferably, on the postal zip codewhere the system 20 will be used. Thus, a purchaser may install such asystem in Mississippi or in California and enter the informationrequired to initialize the system, including the zip code where thesystem is to be used, and the date. In each case the information in thedatabase allows the microprocessor 30, by using the database 34, toperiodically select the duration of actual irrigation (Dactual) for anyparticular sector in a way that is rationally and efficiently based onthe changing seasonal ET rate in the selected sector, and accounts forlikely rainfall, and for dry, hot, and windy conditions. This aspect ofthe invention has the considerable advantage of relieving the user ofresponsibility for manually adjusting the duration for irrigation everyperiod, which a user typically may forget to do after a few adjustments.It also has the advantage of achieving a result that is very similar toa result in which a sprinkler system uses a sensor device to measure theactual environmental conditions for adjustment based on actualenvironmental conditions, while avoiding all the disadvantages includingthe cost of such systems.

Thus, it will be apparent from the foregoing that, while particularforms of the invention have been illustrated and described, variousmodifications can be made without parting from the spirit and scope ofthe invention.

1-16. (canceled)
 17. A controller for controlling an irrigation schedulein an irrigation system, the irrigation system including a plurality ofsprinkler heads connected via a plurality of conduits to a water source,the controller comprising: a database that includes information relatingto historical evapo-transpiration rates for a plurality of sectorslocated within a geographical area, the information including thehistorical period-average evapotranspiration rate for each period of theyear per sector, and the maximum period-average evapotranspiration ratethat occurs in one year per sector; an input means for permitting a userto enter irrigation parameters into the controller, wherein theparameters include: a Maximum Irrigation Duration; an identifier foridentifying the sector in which the irrigation system is located; andthe current date; and a microprocessor configured to divide, for eachsector, the historical period-average evapotranspiration rate for eachperiod of the year by the maximum period-average evapotranspiration rateto provide a Period Reduction Factor for each sector, and being furtherconfigured to adjust the Maximum Irrigation Duration that has beenentered into the controller by multiplying the Maximum IrrigationDuration by the Period Reduction Factor for the current periodassociated with the sector that has been identified by the user, toobtain an Actual Irrigation Duration for the current period for theidentified sector, the microprocessor being further configured to causethe irrigation system to irrigate for the Actual Irrigation Durationduring the current period.
 18. The controller of claim 17, wherein thesector identifier is a zip code.
 19. The controller of claim 17, whereinthe sector identifier is a county name.
 20. The controller of claim 17,wherein the sector identifier is a city name.
 21. The controller ofclaim 17, wherein the microprocessor is configured to sequentiallyrecalculate the Actual Irrigation Duration in each new period byapplying the Period Reduction Factor associated with each new period,and causing the irrigation system to irrigate for the Actual IrrigationDuration during the new current period.
 22. The controller of claim 17,wherein the period associated with the Period Reduction Factor is amonth.
 23. The controller of claim 17, wherein the period associatedwith the Period Reduction Factor is a week.
 24. The controller of claim17, wherein the period associated with the Period Reduction Factor is aday.
 25. A method of controlling the duration of irrigation by anirrigation system that includes a plurality of sprinkler heads connectedvia a plurality of conduits to a water source, the method comprising:compiling a database that includes information relating to historicalevapo-transpiration rates for a plurality of sectors located within ageographical area; entering irrigation parameters into the controller,wherein the parameters include: a Maximum Irrigation Duration; anidentifier for identifying the sector in which the irrigation system issituated; and the current date; deriving, from the information, PeriodReduction Factors applicable over a year for a sector identified by auser, wherein the Period Reduction Factors are derived as the historicalperiod-average evapotranspiration rate for each period of the year,divided by the maximum period-average evapotranspiration rate thatoccurs in a year for the identified sector; adjusting the MaximumIrrigation Duration by multiplying the Maximum Irrigation Duration by aPeriod Reduction Factor for the current period, to obtain an ActualIrrigation Duration for the current period for the identified sector;and causing the irrigation system to irrigate for the Actual IrrigationDuration during the current period.
 26. The method of claim 25, whereinentering a sector identifier into the controller includes entering a zipcode.
 27. The method of claim 25, wherein entering a sector identifierinto the controller includes entering a county name.
 28. The method ofclaim 25, wherein entering a sector identifier into the controllerincludes entering a city name.
 29. The method of claim 25, wherein theperiod associated with the Period Reduction Factor is one month.
 30. Themethod of claim 25, wherein the period associated with the PeriodReduction Factor is one week.
 31. The method of claim 25, wherein theperiod associated with the Period Reduction Factor is one day.
 32. Themethod of claim 25, wherein adjusting the Maximum Irrigation Durationincludes sequentially recalculating the Actual Irrigation Duration ineach new period by applying the Period Reduction Factor associated witheach new period, and causing the irrigation system to irrigate for theActual Irrigation Duration during the new current period.